afaik, they were very expensive and very rare - these things weren't imported officially, you prolly could only get it from somebody you knew from a famous band or smth at terribly overblown black market prices.
I remember from a docu about polish rock band czerwone gitary where they say after a few first concerts in soviet union they were afraid to take their best instruments with them. local musicians would stalk them and get into their hotel rooms offering ridiculous money for like a fender guitar, money so high they would find hard to resist and would sell their favorite pieces. that's from what I know pretty much how scarce any of western or japanese instruments were.
and yeah some of the biggest the top pop stars and composers and tv and radio studios etc were able to furnish whole studios by ordering whatever they needed officially, I guess they would be granted they need that to keep churning out the right stuff.